Do not cap at DEFAULT_BUFFER_SIZE

Author: marcelm

Lib/_pyio.py

@@ -1001,7 +1001,7 @@ def peek(self, size=0):
             raise ValueError("peek on closed file")
         if size < 1:
             return self._buffer[self._pos:self._pos + DEFAULT_BUFFER_SIZE]
-        return self._buffer[self._pos:self._pos + min(size, DEFAULT_BUFFER_SIZE)]
+        return self._buffer[self._pos:self._pos + size]
 
     def truncate(self, pos=None):
         if self.closed:

Lib/test/test_io/test_memoryio.py

@@ -609,12 +609,6 @@ def test_peek(self):
             self.assertEqual(memio.peek(len(abc) + 100), abc)
             self.assertEqual(memio.tell(), len(buf))
 
-        # Length of returned bytes object is capped to DEFAULT_BUFFER_SIZE
-        buf = self.buftype("a" * (io.DEFAULT_BUFFER_SIZE + 10))
-        with self.ioclass(buf) as memio:
-            self.assertEqual(len(memio.peek()), io.DEFAULT_BUFFER_SIZE)
-            self.assertEqual(len(memio.peek(io.DEFAULT_BUFFER_SIZE + 1)), io.DEFAULT_BUFFER_SIZE)
-
         with self.ioclass(buf) as memio:
             memio.seek(len(buf))
             self.assertEqual(memio.peek(), self.EOF)

Modules/_io/bytesio.c

@@ -529,9 +529,7 @@ _io_BytesIO_peek_impl(bytesio *self, Py_ssize_t size)
 
     /* adjust invalid sizes */
     Py_ssize_t n = self->string_size - self->pos;
-    if (n > DEFAULT_BUFFER_SIZE) {
-        n = DEFAULT_BUFFER_SIZE;
-    }
+
     if (size < 1 || size > n) {
         size = n;
         /* n can be negative after truncate() or seek() */